The overall goal of this proposal is to improve the medical decision-making process by providing computer assistance to the physician. Efforts are proposed in two specific areas: 1) medical decision logic is being developed to accurately predict the pre-test likelihoods of possible findings of X-ray examinations. This knowledge is necessary to evaluate efficacy and utility of radiological tests; 2) decision analysis will be used to evaluate the expected utility (based on costs and benefits) of alternative tests or therapies which may be considered for patients with coronary artery disease. Decision analysis will be performed when any of the following data are added to the computerized patient data base: 1) history of angina; 2) results of an EEG stress test; and 3) results of a selective coronary arteriogram. The system is designed to provide the physician with a "virtual memory" which contains the results of current medical literature and expertise of consultants. The medical knowledge to accomplish these tasks will be stored in the form of patient-specific decision algorithms. This logic will contain accurate probability distributions for disease attributes and predictive values of diagnostic tests as well as quantitative data necessary to make decisions based on optimal expected utility. These data will be obtained from current medical literature and by analysis of a computerized patient data base. The HELP system for medical decision-making developed at LDS Hospital will furnish the primary framework for this project.